Unloading conveyors for harvesters such as combines typically take the form of an unloading tube in which a power driven unloading auger is disposed. The unloading conveyor with which this invention is concerned has a transport position wherein the unloading tube is swung to a position alongside the combine and is swingable under the influence of power means to an upwardly and outwardly extending position in which the grain bin can be conveniently unloaded into a truck or trailer pulled alongside the combine. The auger within the loading tube is typically driven through a universal connection disposed at the pivot joint for the unloading tube. When the unloading tube is within a range of an outwardly extending unloading positions, there is sufficient augularity between the driving and driven components of the universal joint to safely transmit power. However, when the unloading tube is swung inwardly to its transport position, the angularity between the driving and driven components of the universal joint is at a virtual right angle relationship wherein power cannot be transmitted through the universal joint without it being broken.